It seems Isle has just altered the ZDoom KDiZD map (by KDiZD team), warped to in the KDiZD intermission screens, into a playable variant, adding player starts and removing the scripts.
To play it, run ZDoom with KDIZD.PK3 and INTER.WAD (the file described), and warp to E1M1 ("-warp 1 1", "idclev11", "map e1m1"). The file itself is hosted on Naked Snake's server: http://bbg.ath.cx/inter.zip
While trying it, also check the areas outside the main view, through no-clipping mode, specifically the underground area and all. There are no monsters though.
Seen from above, this map (by team KDiZD originally) tries alot to imitate the original WIMAP0 picture, though the blinking lights present in WIMAP0 haven't made it here.